1. Field of the Invention
This invention relates to a method of stabilizing an organic substrate material against the action of light, and, more particularly, to a method for stabilizing an organic compound such as an organic dyestuff. Still more particularly, the present invention relates to a photographic material containing a specific compound to improve the light fastness of the photographic dye images.
2. Discussion of the Prior Art
As is commonly known, organic substrate materials, for example, organic dyes, tend to fade or undergo discoloration by the action of light. Accordingly, in the fields of ink technology, textile dyeing or color photography, extensive studies are being carried out in order to prevent such fading or discoloration, i.e., improve the light fastness of organic dyes. The instant invention can be applied for such purposes.
In the present specification, the term "organic substrate" or "organic substrate material" means substances which appear colored or colorless to the human eye under the illumination of sunlight and which have an absorption peak in the visible spectrum or even in the infrared region including optical whitening agent. Thus, the organic substrate materials of the instant invention include organic substances having an absorption maximum in the spectral region between about 300 nm (in the UV region) and about 800 nm (in the infrared region). These organic substrate materials occur particularly in photographic materials, e.g., color films, prints, diffusion transfer units, etc., in colored polymers useful as agricultural vinyl cover sheets, umbrellas, tents, etc.; fluorescent whitening agents; and dyed textiles, etc., and this invention is directed to improving the light fastness of these materials in each of these environments.
In the following description of the present specification, the term "dye" or "dyestuff" implies organic substances which appear colored to the human eye under the illumination of sunlight.
The word "light" in the specification means electromagnetic radiation with wavelengths up to about 800 nm, including ultraviolet light up to about 400 nm, visible light between about 400 and about 700 nm and infrared light between about 700 nm and about 800 nm.
It is widely accepted that organic substrate materials such as dyes tend to fade or change color upon exposure to light, and a large number of reports have been published on methods of retarding or reducing such fading or discoloration, i.e., of improving the light fastness of dyes. For example, U.S. Pat. No. 3,432,300 discloses one such method in which a phenol derivative having a fused heterocyclic structure is mixed with organic compounds such as indophenol, indaniline, azo and azomethine dyes to improve the fastness to visible as well as ultraviolet light.
Generally speaking, in the field of silver halide photographic materials, azomethine or indaniline type dyes are formed as the result of the reaction between the oxidation product from an aromatic primary amine developing agent and a color forming coupler, as is described in Chapter 17 of The Theory of the Photographic Process authored by C. E. K. Mees and T. H. James (Macmillan Co., 1967). Many methods have been proposed to improve the light fastness of the color images comprising such types of dye. Fade preventing or retarding agents conventionally used include hydroquinone derivatives disclosed in U.S. Pat. Nos. 2,360,290, 2,418,613, 2,675,314, 2,701,197, 2,704,713, 2,728,659, 2,732,300, 2,735,765, 2,710,801 and 2,816,028, U.K. Pat. No. 1,363,921, etc., gallic acid derivatives set forth in U.S. Pat. Nos. 3,457,079 and 3,069,262, Japanese Patent Publication No. 13,496/1968, etc., p-alkoxyphenols set forth in U.S. Pat. Nos. 2,735,765 and 3,698,909, chroman and coumarane derivatives set forth in U.S. Pat. Nos. 3,432,300, 3,573,050, 3,574,627, 3,764,337, 3,574,626, 3,698,909, 4,015,990, etc. However, these cited compounds can prevent fading or discoloration only to some extent but not to satisfactory degree.
Further, U.K. Pat. No. 1,451,000 discloses another method of stabilizing organic substrate materials against the action of light based on the use of an azomethine quenching compound which has an absorption maximum at a wavelength longer than that of the substrate material; unfortunately, such azomethine quenching compounds are ordinarily deeply colored by themselves, thus, adversely affecting the color phase of the substrate material.
Degradation of polymeric substances can be prevented by the use of metal chelates; reference should be made to J. P. Guillory and R. S. Becker, J. Polym. Sci., Polym. Chem. Ed., 12, p. 993 (1974) and R. P. R. Ranaweera and G. Scott, J. Polym. Sci., Polym. Lett. Ed., 13, p. 71 (1975). Further, a method of stabilizing dyes with metal complexes is described in Japanese Patent Application (OPI) No. 87,649/1975 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application") and Research Disclosure 15162 (1976). These complexes, however, do not exhibit sufficient fade preventing capability and are poorly soluble in organic solvents. The latter property prohibits incorporating the complexes at the high concentrations required for complete fade prevention. In addition, the considerable color of these complexes deteriorates the color hue and the color purity of the substrate material when they are used in higher concentrations.
Furthermore, fade preventing agents capable of improving the light fastness of cyan dyes have not been known.